Until very recently windows for use in sailboats, motorboats, yachts, camper trailers, house trailers and the like were fabricated of glass mounted in metal frames. For large boats, such as luxury yachts, the frames are made of brass, stainless steel or other corrosion resistant metal. These frame materials, however, are quite expensive and their use is not justified in the smaller windows required for sailboats, motorboats and camper trailers, for example. In smaller recreational vehicles, such as boats, camper trailers and the like, it is current practice to fabricate the window fames of bent extruded aluminum shapes. Aluminum, however, is susceptible to corrosion, especially in salt atmospheres such as are encountered in marine applications. Corrosion of aluminum window frames may be prevented by painting the frame, but this maintenance effort is not always pursued; also, paint does not adhere readily to aluminum, with the result that where a diligent painting program is pursued the window frames must be repainted frequently.
Recently, in an effort to overcome the disadvantages associated with aluminum frames, a window having a frame fabricated of thermoplastic material has recently been introduced commercially for use in small boats. This product has a pane of transparent synthetic resin and a one-piece frame fabricated of vacuum-formed ABS resin to which the pane is bonded. Because the frame is fabricated by vacuum forming techniques, the thickness of the frame material is necessarily relatively thin. Accordingly, these windows flex readily and the bond between the pane and the frame may break in response to such flexing. These windows have the advantage that they are made entirely of synthetic materials which are resistant to corrosion and which can be colored to harmonize with the remaining structure in which they are installed. These windows, because of their one-piece frame construction, are either bonded or screwed to the basic boat structure peripherally of the window opening. Where provided, an interior trim frame is merely bonded or screwed to the interior of the boat structure for the purposes of ornamentation. The trim frames have no structural cooperation with the support frame for the pane, and are not relied upon to mount the window in the window opening.
Because the pane supporting frames of the aforementioned all-synthetic windows are formed by vacuum forming techniques, the cross-sectional configuration of the frame necessarily must be simple. The complex cross-sectional shapes achievable in extrusions cannot be formed by vacuum forming techniques. Accordingly, existing all-synthetic resin windows are not openable in that the transparent pane of these windows is bonded to the supporting frame entirely around the periphery of the pane. An advantage of the more expensive windows having stamped or extruded frames is that such windows can have a fixed pane, a second movable openable pane and, if desired, a screen; these features are not possible where the frame is fabricated by vacuum forming or similar techniques.
It is known that attempts have been made to provide a window for camper trailers, boats and the like wherein the window frame is defined by an extruded rigid synthetic resin. These attempts sought to realize the increased advantages of a window having an extruded frame; these advantages include the ability to provide openable windows with or without screens and the increased structural strength obtainable with an extruded frame, thereby providing a window frame which does not flex and separate from the pane. These prior attempts were not successful, and it is believed that these failures were caused by the difficulties attendant to bending the normally straight extrusion into the appropriate curvature necessary for these types of windows. Aluminum is readily extrudable into myriad shapes of complex cross-sectional configuration, and these extrusions are bendable from a straight into a curved shape by techniques similar to the techniques used inpipe bending, for example. These techniques are dependent upon the cold-flowability of aluminum under extreme loads. Synthetic resins having the desired characteristics of rigidity and strength, however, do not possess these cold-flowable characteristics, with the result that techniques found successful for the bending of aluminum extrusions cannot be adapted to the bending of extrusions fabricated of synthetic materials such as rigid thermoplastic resins.
It is apparent from the foregoing, therefore, that a need exists for the provision of windows for boats, camper trailers and the like, in which the window frame is fabricated of an extruded synthetic material. Similarly, in order that these producets may be produced, a need exists for the developement of processes and equipment for the bending of rigid thermoplastic shapes without fracture of the thermoplastic material and without loss of the cross-sectional configuration defined by the shape.